The main road in Belleville is 7 3/10 miles long.
so far 2 3/4 miles have been repaved. How many miles 
have not been repaved?

 7 =   7  =  6
-2  =  -2  = -2
———————————————————————
                  4

The first step was to get the least common denominator
of 10 and 4.  Since 20 is the smallest positive integer
that both 10 and 4 will divide into evenly, 20 is the
LCD. So we changed the  to  and changed the
 to .  Then we noticed that the upper
fraction  was smaller than the lower fraction
, so to make the upper fraction larger, we 
borrowed 1 from the 7 leaving it as 6, then took the 1 that 
we borrowed, thought of it mentally as  
and added it to the  making it .  Then 
we merely subtracted the whole parts and the fraction parts.

Edwin